Polarization equipment and data measured
cooperation with Research Institutes, one University in France with a Shock Laboratory in Bretagne, ENSTA Bretagne (Professor Michel Arrigoni ENSTA – Bretagne 2 Rue François Verny
29806 Brest Cedex 9 FRANCE) and one other University in Mulhouse (Dr. Mohamed Bouraoui KECHICHE Ecole Nationale Supérieure des Ingénieur Sud Alsace Université de Haute Alsace 11 rue Alfred Werner - 68093 Mulhouse Cedex France) new sensors, actuators and prototypes are developed.
AIFP has the equipment for applying an electric field to these ferroelectric materials "polymers".and for poling specific areas in precise manner. This pilot line will be identical to that one who was developed at ISL (patent of F. Bauer).
hysteresis curves obtained on the polymer subjected to a predetermined electric field allow to determine the following data:
Id induction current in A
Ip: A bias current
P: Polarization in C/m²
D: induction electric C/m²
εr: relative permittivity
Stored Electrical Energy in J/m3
AIFP can determine with his piezometer equipment d and g piezoelectric coefficients.
Examples of Data and Hysteresis cycles
For example, Figure 1, a PVDF film 22 microns thick biaxially oriented requires an electrical field of 400V/μm for being poled at levels between 7 and 9 mC/cm ².
Figure 1. Induction (orange curve) Polarization (blue line), polarization current (green curve) as a function of the electric field. The value of the remnant polarization PR is at the intersection of the curves D (E) and P (E). When D = P = 0, it is easily to determine the coercive field Ec.
For P(VDF-TrFE) copolymer
The data obtained from the hysteresis curve of the polarization of one copolymer P(VDF-TrFE) are shown below. Electrical fields must range from of 60V/µm up to 100 V/µm in order to obtain polarization values of the order of 6 mC/m², Fig. 2.
Figure 2. Hysteresis loops for a copolymer.
2 a. Polarization (blue curve), polarization current (green curve). 2b. D (induction orange) and εr (black) versus electric field.
For a terpolymer of VDF (vinylidene difluoride) TrFE (trifluoroethylene) and CFE (chlorofluorocarbons 1.1, ethylene) or CTFE (chlorotrifluoroethylene), the gradual transition from the conformation tttg + tttg + conformation (γ phase) to the all-trans conformation (β phase) occurs at an electric field of 20 MV/m and is complete at 150 MV/m, where the spontaneous polarization is approximately equal to 3.5 mC/m ², Fig. 3a and 3b.
Figure 3. Hysteresis loops for a terpolymer.
3a. D (induction orange) and εr (black) versus electric field. 3b. Polarization (blue curve), polarization current (green curve).